Influence of the maturity of the seeds and the stem on the phenolic composition of the wine

Identifier:  TFM:273

Handle: https://hdl.handle.net/20.500.11797/TFM273

Authors:  Conde Chijeb, Marta

Abstract:
The aim of this study is to evaluate the influence of the ripening of the seeds and the stems on the phenolic composition of the wine. Five different vinifications are made at 3 levels of maturity with two varieties (vitis vinifera cv. Merlot and Tempranillo) The vinifications were carried out with must, must and seeds, must and stems, grapes crushed without stem; and grapes crushed with stem. Afterwards, the phenolic composition and the color of the resulting wine are analyzed after alcoholic fermentation (malolactic fermentation is avoided). The seeds contribute mainly (+) - catechin, (-) - epicatechin and proanthocyanidins of low mDP and high percentage of galloylation. Its extraction is greater in green vintages. Stems provide (+) - catechin and (+) - gallocatechin, proanthocyanidins with higher mDP and prodelphidins. Winemaking with seeds and stems increase the pH of the wine and decrease its alcoholic strength. These effects are more pronounced with the stems. In the vinifications with stems the PVPP Index increases; and the Ionization Index and the Index of copigmentation (with respect to the destemmed grape) decrease. It also decreases the color intensity. With a higher level of maturity increases the IPT, the mDP of the proanthocyanidins and the content in anthocyanins. In order to better quantify the effects of the maturity level of the vintages on the composition of the wine, it would be necessary to distance the vintages more and avoid overripe.